Shellfish dominate the list of iron-rich seafood, with oysters, mussels, and clams delivering several times more iron per serving than most fish. Three oysters provide about 6.9 mg of iron, which covers nearly 40% of the daily need for premenopausal women and close to a full day’s worth for men. If you’re looking to boost your iron intake through seafood, the general rule is simple: shells beat fins.
Shellfish: The Iron Heavyweights
Oysters sit at the top. A 3-ounce serving of cooked wild eastern oysters contains roughly 7.8 mg of iron. Even raw farmed oysters deliver about 4.9 mg per 3-ounce serving. The preparation method matters: oysters cooked with moist heat retain more iron than breaded and fried versions, though both are still excellent sources.
Mussels come in a close second. A cup of raw blue mussels contains about 5.9 mg of iron, and a standard 3-ounce cooked portion provides around 5.7 mg. Mussels are also widely available, relatively affordable, and quick to cook, making them one of the most practical high-iron foods you can buy.
Clams are where things get complicated. USDA data lists canned clams as a top iron source, but a closer look reveals enormous variation. A study analyzing canned clam products from major supermarkets found iron content ranging from less than 1 mg to nearly 60 mg per 100 grams of drained product. Whole baby clams averaged 30.5 mg per 100 grams, while chopped or minced versions averaged just 1.4 mg. The researchers concluded that minced clams shouldn’t be considered a reliable iron source, and the whole baby clams raised separate concerns about aluminum contamination. If you’re buying canned clams for iron, the type and brand matter far more than you’d expect.
Octopus is another strong option at 4.5 mg per 3-ounce raw serving, though it’s less commonly eaten in everyday meals.
Crab, Shrimp, and Other Crustaceans
Crustaceans contain less iron than mollusks but still contribute meaningful amounts. Queen crab delivers about 2.5 mg per 3-ounce cooked serving. Shrimp provides 1.8 mg per serving, and spiny lobster comes in at 1.2 mg. These won’t cover your daily needs on their own, but they add up when combined with other iron-rich foods in the same meal.
Where Fish Rank
Most fin fish fall well below shellfish in iron content. Sardines are the standout among common fish, providing about 2.5 mg per 3-ounce canned serving. After that, the numbers drop off: skipjack tuna has 1.36 mg, mahi-mahi 1.23 mg, trout about 1.19 mg per fillet, and pickled herring 1.71 mg per cup. These are modest amounts compared to what a few oysters or a bowl of mussels can deliver.
If fish is your main protein, sardines are the clear winner for iron. They’re also inexpensive, shelf-stable, and low in mercury. But if you’re specifically eating seafood to address an iron gap, shellfish will get you there faster.
Why Seafood Iron Absorbs Well
Iron in food comes in two forms. Heme iron, found in animal tissues, is absorbed efficiently by your body. Non-heme iron, found in plants and fortified foods, is harder to absorb. Seafood contains both types, with 25 to 65 percent of the iron in fish and shellfish being the more absorbable heme form.
Not all shellfish are equal in this regard. Blood clams contain about 10 times more heme iron than Manila clams and 7 times more than Pacific oysters. In fact, blood clams have 1.6 times the heme iron of beef liver, which is often cited as the gold standard for dietary iron. Most people won’t encounter blood clams at their local grocery store, but if you see them at an Asian market, they’re worth knowing about.
Pairing any seafood with a source of vitamin C at the same meal helps your body absorb the non-heme portion of the iron more effectively. A squeeze of lemon over steamed mussels or a side of bell peppers with grilled fish isn’t just a flavor choice. It has a measurable effect on how much iron you actually take in.
How Much Iron You Actually Need
Adult men and postmenopausal women need about 8 mg of iron per day. Premenopausal women need 18 mg, and pregnant women need 27 mg. That gap between 8 and 18 mg is exactly why iron deficiency is far more common in women of reproductive age.
To put this in perspective: a serving of six oysters gets a man past his daily target and covers about 77% of a premenopausal woman’s needs. A serving of mussels alongside some sardines and a vitamin C-rich side dish could close the gap entirely for most people. For those with higher needs, shellfish a few times a week makes a real dent.
Mercury Isn’t a Concern With High-Iron Shellfish
The seafood highest in iron also happens to be among the lowest in mercury. FDA testing data shows clams averaging just 0.009 parts per million of mercury, which is nearly undetectable. Oysters, mussels, and shrimp are similarly low. This is because these species are filter feeders or small organisms low on the food chain, so they don’t accumulate mercury the way large predatory fish do. You can eat high-iron shellfish frequently without worrying about the contaminant concerns that apply to tuna or swordfish.
Quick Comparison by Serving
- Oysters (3 oz cooked): 6.9 to 7.8 mg
- Mussels (3 oz cooked): 5.7 mg
- Octopus (3 oz raw): 4.5 mg
- Sardines (3 oz canned): 2.5 mg
- Crab (3 oz cooked): 2.5 mg
- Clams (3 oz, varies widely): 0.9 to 2.4 mg
- Shrimp (3 oz cooked): 1.8 mg
- Tuna, skipjack (3 oz cooked): 1.4 mg
- Mahi-mahi (3 oz cooked): 1.2 mg